Using the [Verification] function in the [Signature/Seal] menu, you can verify the signatures and timestamps applied to a PDF file.
Before verifying the signatures and timestamps applied to a PDF, please check the following:
When you select [Verification] in the [Signature/Seal] menu, the signature history screen is displayed, and you can check the history of signatures and timestamps applied to the PDF.
Verify
Select one of the displayed histories and press [Verify] to verify the selected signature/timestamp.
Also, if a signature/timestamp imprint is displayed on the PDF, you can also verify it by clicking the imprint.
Press [Property of signature] on the signature verification status screen to check the details of the verification result. (See: About Verification Results)
[PAdES] Tab in Property of Signature
When you open the [PAdES] tab in property of signature, you can check the next action and its deadline required for long-term assurance of that signature.
Adding Verification Information
Select one of the displayed histories and press [Add Verification Information] to embed the current verification information of the selected signature/timestamp in the PDF.
If you press [Add Verification Information] without selecting any of the displayed histories, the current verification information of all signatures/timestamps will be embedded in the PDF.
Displaying Signature History Generations
Right-click one of the displayed histories and select [View in this state] to check the display of the PDF when the signature was added and the difference display from other signature points.
Generations are updated each time a signature is added and saved (incrementally updated) to the PDF.
You can trace back from the current (latest version) to version 1, which was added first.
If you check [Show the difference from the selecting generation] while selecting the generation to compare, you can check the difference between the two versions.
When verifying, an error message may be displayed and it may not be possible to verify normally.
Usually, the error is as notified in the message, but there may be a similar error if the specified signature verification method is not suitable for the signature format.
Open the [Verification settings] in the [Signature] tab in Preferences, uncheck [Specify the verification method.], and try verifying again.
When verification is performed, checks are made to ensure that the data has not been tampered with, the document has not been modified, and the certificate used is trustworthy.
The status of the verification results in this product is primarily displayed in the following five patterns:
“Valid” is a verification result that indicates that there have been no changes to the document after the timestamp or signature has been applied.
“Valid (extended)” is a verification result that indicates that there have been no changes to the document after the timestamp or signature has been applied, and an archive timestamp has been added.
“Falsification” is a verification result that indicates that some changes have been made after the timestamp or signature has been applied.
If the internal data that is the target of the signature/timestamp is in a different state than when it was applied, it will be detected as falsification.
Note that the result of falsification (changing the target data) may not appear in the appearance of the PDF.
In addition to data forgery, if changes have been made to the target data due to reconstruction saving (See: About Incremental Update and Reconstruction) after PDF editing, it will also be detected as falsification.
“Append” is a verification result that indicates that some changes have been made after the timestamp or signature has been applied.
However, unlike falsification, there are no changes to the internal data that is the target of the signature/timestamp in the case of append. It refers to the state where new data related to the changes has been added at the end of the file, that is, after the signature or timestamp.
Note that the result of append (adding change data) may not appear in the appearance of the PDF.
To save as append rather than falsification after editing a PDF with a signature or timestamp applied, you need to perform incremental update saving (See: About Incremental Update and Reconstruction).
Also, in the case of a PDF to which only an invisible Amano timestamp has been applied, unlike other signatures and timestamps, ‘additional verification information’ is also considered as append.
If you set ‘SKYCOM Standard Signature’ as the verification method, you can obtain a normal verification result without considering it as append.
(To change the verification method, go to Preferences > [Signature] tab > [Verification settings] > [Specify the verification method.])
“Unknown” is a verification result that indicates that verification could not be performed normally for some reason, such as lack of certificates or network failure.
Also, signatures applied using electronic certificates stored in My Number cards can only be verified by specific entities such as administrative agencies (like the National Tax Agency, Patent Office, etc.) and certain private businesses certified by the Minister of Internal Affairs and Communications. Therefore, these signatures are displayed as ‘unknown’ in general verification results.
“Incremental update saving” is a saving method that maintains existing internal data as it is and adds new data related to changes to the end.
New signatures and timestamps, annotations, text, image additions or changes, deletions, etc., are added every time you save, regardless of the content of the changes.
For example, if you delete a page and perform incremental update saving, the existing data, including the data of the deleted page, remains as it is, and the data of “The page ‘X’ has been deleted” is newly added, so the file size is larger than before the page deletion.
“Reconstruction saving” is a saving method that reconstructs and saves all elements that make up the PDF, including signature target data and signature data itself.
For example, if you delete a page and perform reconstruction saving, it will be reconfigured as a new PDF without data related to the deleted page, so the file size is smaller than before the page deletion.
The following edits and operations require reconstruction saving:
Whether changes to the PDF are saved by incremental update or reconstruction depends on the specifications and settings of the application you are using.
In SkyPDF products, changes to PDFs with signatures/timestamps applied are saved by incremental update regardless of the settings, and edits and operations that require reconstruction saving, such as changes to security settings, are restricted except for some exceptions.